This is what I thought. Like you said before, there's obviously no way to ever actually "lock" at a rank, so I suppose you could infinitely extend the number of wins on a 50. I guess the difficulty just lies in the fact that 50s will at best receive theoretically "even" matches against other 50s, since they can never play against someone higher. Again, none of this is actually relevant in the slightest; I just thought it was an interesting discussion topic.